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1.
Inhalt: Nach Steuerung der Ovarfunktion beim Rind mit PMSG/PGF2α und FSH/PGF2α war 6.5 h nach der PGF2α-Applikation eine deutliche Abhängigkeit zwischen den Estradiol-17β (E2)- bzw. Testosteron (T)-Konzentrationen in der Follikelflüssigkeit und der Gröβe der Ovarialfollikel zu erkennen. In präovulatorischen Follikeln wurden unabhängig von der gewählten Hormonbehandlung teilweise signifikant höhere (P < 0,05) mittlere E2- und LH-Konzentrationen als in nonovulatorischen Follikeln festgestellt. Follikel mit intakten oder degenerierten Oozyten wiesen keine signifikanten Unterschiede im Steroidgehalt auf. Der Reifungsprozeß der Cumulus-Oozyten-Komplexe bzw. Oozyten war mit charakteristischen Verschiebungen in den intrafollikulären Hormonspiegeln verbunden. Auch die veränderten Verhältnisse der Steroidhormonkonzentrationen in der Follikelflüssigkeit bestätigen die Rolle der Steroide bei der Oozytenreifung.  相似文献   

2.
Prostaglandin F2α receptors (PGF2α Rs) were measured in bovine corpus luteum and myometrial cell membranes using a radiometric method. The inhibition of labelled PGF2α binding exerted by d-cloprostenol, dl-cloprostenol, PGF2α and PGE1 (l0–11 M to 10–4 M) was evaluated in vitro. Results strongly suggest that cloprostenol binding to PGF2αRs is stereospecific. d-Cloprostenol and PGF2α were equipotent, about 150 times more potent than d-cloprostenol (P < 0.05) and approximately 280 times more potent than PGE, (P < 0.05) in inhibiting [3H]PGF2α binding to corpus luteum cell membranes. Such differences were less evident in myometrial cell membranes, where d-cloprostenol and PGF2α were about 10 times more potent than d-cloprostenol (P < 0.05) and approximately 95 times more potent than PGEl (P < 0.05).  相似文献   

3.
Contents: In this review, the role of eicosanoids in regulation of parturition and the postpartum period was described with special emphasis on the bovine species. The metabolism of arachidonic acid and the production of eicosanoids during the peripartum period was discussed. Prostaglandin E2 and F2α (PGE2, PGF2α) play an important role in mechanisms controlling parturition. They are involved in luteolysis, uterine contractions and dilation of the cervix. Eicosanoids also seem to influence the loosening processes of the fetal membranes. However, in the literature, conflicting results were found. Many investigations suggested that retained placental membranes could be related to low PGF2α production and/ or an imbalance of arachidonic acid metabolism in the uterus. The possible role of the lipoxygenase pathway metabolite 15-hydroxy-eicosatetraenoic acid (15-HETE) in expulsion of the fetal membranes was also discussed. As far as the postpartum period is concerned, a relationship between postpartum PGF2α release and the involution of the uterus was found. Cows with undisturbed uterine involution had higher PGF2α production than cows with delayed involution. In contrast to the positive effect of PGF2α on uterine involution, PGE2 seems to delay the involution processes. Further experiments are necessary in order to study the function of eicosanoids in mechanisms regulating parturition, release of the fetal placental membranes and involution of the uterus.  相似文献   

4.
Isolated sheep lung parenchymal strips responded to histamine > carbachol > PGF2a > 5-HT with contractions, and to isoproterenol (Isop), and to large doses of epinephrine (E), norepinephrine (NE) and phenylephrine (PE) with relaxations. PGF2a-contracted lung strip responded to PGE1 and PGE2 with relaxation. The strips which were partially contracted to histamine, PGF2a, 5-HT and carbachol also responded to isop, E and NE with relaxations. Histamine responses were not modified by metiamide (an H2-receptor antagonist). Mepyramine and atropine selectively antagonized contractions to histamine and carbachol, respectively. After β-blockade with propranolol, lung strips responded to NE > E > PE > isop with contractions, which were inhibited or reversed by phentolamine and dibenzyline. It is concluded that H1 receptors are present in sheep peripheral airway smooth muscles, and that a- and β-adrenoceptors mediate contraction and relaxation, respectively, in sheep lung strips.  相似文献   

5.
α2-adrenoceptor agonist drugs can cause respiratory changes leading to a short period of hypoxaemia in sheep. It has been suggested that this is due to transient platelet aggregation and pulmonary microembolism. If platelet aggregation were to follow platelet activation in response to the administration of α2 agonists, plasma thromboxane levels would be expected to rise. This study was carried out to measure plasma thromboxane B2 concentrations before and after the intravenous administration of the α2-agonist drug xylazine at a dose of 0.1 mg/kg. It was found that the plasma thromboxane concentration rose by 320% and, furthermore, the rise was prevented by the prior administration of atipamezole hydrochloride (0.125 mg/kg), an α2-adrenoceptor antagonist.  相似文献   

6.
α2-Adrenergic receptor agonists are widely used in veterinary medicine as sedative/hypnotic agents. Four pharmacological subtypes of the α2-adrenergic receptor (A, B, C and D) have been identified based primarily on differences in affinity for several drugs. The purpose of this study was to examine the affinities of the sedative agents, xylazine, detomidine and medetomidine at the four α2-adrenergic receptor subtypes. Saturation and inhibition binding curves were performed in membranes of tissues containing only one subtype of a2-adrenergic receptor. The KD for the α2-adrenergic receptor radioligand, [3H]-MK-912, in HT29 cells (α2A-), neonatal rat lung (α2B-), OK cells (α2C-) and PC12 cells transfected with RG20 (α2D-) were 0.38 ± 0.08 n m , 0.70 ± 0.5 n m , 0.07 ± 0.02 n m and 0.87 ± 0.03 n m , respectively. Detomidine and medetomidine had approximately a 100 fold higher affinity for all the α2-adrenergic receptors compared to xylazine but neither agonist displayed selectivity for the α2-adrenergic receptor subtypes. These data suggest that available sedative/hypnotic α2-adrenergic receptor agonists can not discriminate between the four known α2-adrenergic receptor subtypes.  相似文献   

7.
Prostaglandin F2α (PGF2α) and GnRH treatments given 24 h apart have been shown to result in short oestrous cycles (8–12 days) in some cows and heifers. The differences in responses may depend on the dose of GnRH. Therefore, the effect of the dose of GnRH on occurrence of short cycles and LH response was studied here. Oestrus was induced with dexcloprostenol (0.15 mg) in two groups of Ayrshire heifers. A second luteolysis was induced similarly on day 7 after ovulation; 24 h after PGF2α treatment, the heifers were administered either a high (0.5 mg, n = 15, group T500) or low (0.1 mg, n = 10, group T100) dose of gonadorelin. Blood samples for progesterone analyses were collected daily from the second PGF2α administration to the second ovulation after the PGF2α injection. Beginning 24 h after the GnRH treatment, ovaries were examined by transrectal ultrasonography every 6 h until ovulation, and daily between day 4 and the next ovulation. Five heifers from both groups were sampled for LH analyses via a jugular catheter every 30 min from 1 h before to 6 h after the GnRH administration. Short oestrous cycles were detected in 7 of 10 cases in group T100 and in 12 of 15 cases in group T500. No significant differences in LH responses were detected between the groups. In group T500, the rise in LH concentration tended to be somewhat slower than in group T100. The dose of GnRH (0.1 vs 0.5 mg) did not affect the occurrence of short oestrous cycles and LH response.  相似文献   

8.
Luteolytic mechanisms have evolved in mammals to improve reproductive efficiency. The hormonal interactions that control the onset and progress of luteolysis are complex. They involve endocrine and paracrine signals that link the corpus luteum, uterus and posterior pituitary gland. Current concepts concerning these interactions will be examined in the five major domestic ungulate species commonly raised in Europe and North America (cattle, sheep, goats, pigs and horses). Some of these interactions are similar across species. All five depend on prostaglandin F2α secreted from the uterus, to induce luteolysis. Three hormones, progesterone, estradiol and oxytocin interact to regulate uterine secretion of PGF2α. Oxytocin is an acute stimulus for uterine PGF2α secretion. Progesterone and estradiol interact to regulate uterine secretary responsiveness to oxytocin. Precisely how these hormones interact varies across species.  相似文献   

9.
During the previous decade several studies focused on postpartum treatment with prostaglandin for improvement of reproductive performance in sows. The aim of the study was to investigate the effect of administration of a prostaglandin F2 α (PGF2 α ) analogue in sows within 24–48 h after farrowing on sow and litter performance. In five commercial farms, the sows were randomly assigned to either treatment A (2 ml cloprostenol, PlanateIM) or treatment B (2 ml physiological saline solution, i.m.). Fifteen per cent of all sows were at random selected for progesterone analysis. Litter performance was assessed by measuring pre-weaning mortality and average daily weight gain (ADG). Sow performance was assessed by measuring weaning-to-oestrus interval (WOI), the percentage of sows returning to oestrus and litter size during subsequent farrowing. Administration of a PGF2 α analogue within 24–48 h postpartum had no effect on the rate of progesterone decline measured over 24 h compared with that of the controls. Litter performance and WOI were not affected by treatment. The subsequent litter size in sows of parity seven and more showed a significant difference of 1.98 piglets (p < 0.01) between both groups, to the benefit of the cloprostenol group. In conclusion, administration of a synthetic PGF2 α analogue, cloprostenol, within 24–48 h after farrowing improved litter size at next farrowing in older (≥7 parity) sows.  相似文献   

10.
Spirals of endothelially denuded equine saphenous vein were used to study the pre- and post-junctional effects of medetomidine in vitro . The pD2 values were calculated for noradrenaline (6.7 /pm 0.1), phenylephrine (5.6 /pm 0.1), BHT 920 (6.2 /pm 0.2) and UK 14304 (5.7 /pm 0.2). Medetomidine produced a biphasic response, with a pD21 of 8.2 /pm 0.1 and a pD22 of 5.7 /pm 0.1 in the equine saphenous vein ( n = 6 ). Prazosin (10−7 m) significantly shifted the second phase of the medetomidine concentration-response curve to the right (pD21 was 8.1 /pm 0.2 and pD22 was 5.0 /pm 0.2, P < 0.05). Rings of equine saphenous vein were electrically stimulated to investigate the pre-junctional effects of medetomidine. Increasing concentrations of the α2-adrenoceptor agonist BHT 920 reduced the response to electrical stimulation in a concentration dependent manner to a maximum of 40 /pm 5%. whereas medetomidine (0.1-100 nm) caused a concentration dependent enhancement to a maximum of 490 /pm 150%. These results suggest α1- and α2-adrenoceptors are functional in the equine saphenous vein, but that medetomidine is not acting exclusively as an α2-adrenoceptor agonist.  相似文献   

11.
The effect of xylazine on the isolated sheep trachea and its possible interactions with the α2-adrenergic antagonist, atipamezole, and the anticholinergic agent, atropine, was studied. The mechanical responses of the tracheal preparations were recorded after exposing each one to cumulatively increasing concentrations of xylazine alone or in the presence of atipamezole or atropine.
Xylazine exerted a concentration-dependent contractile effect, with a threshold concentration of 10--7M while the maximum activity was produced at a concentration of 10--5M (EC50= 2.3 × 10--7). This xylazine-induced contractile effect was inhibited by atipamezole, but not significantly modified by atropine. Thus, it is concluded that α2-adrenoceptors exist in the sheep trachea and it is suggested that α2-adrenoceptor agonists may act on airways in sheep directly through stimulation of peripheral α2-adrenergic receptors and indirectly via central α2-adrenergic receptor activation of parasympathetic tone.  相似文献   

12.
We examined the functional role of adrenergic receptor subtypes (ARs) in bovine intra-mammary arteries (IMAs), 1.5–2.5 mm internal diameter. Norepinephrine (NE) and phenylephrine (PE) produced concentration-dependent increases in tone in segments maintained at a previously determined optimal basal tension in vitro . The sensitivity of the tissue to NE and PE, based on -log molar ED50s was 6.87 ± 0.17 and 7.05 ± 0.35, respectively. In addition a Schild analysis yielded antagonist affinities for the receptor mediating contractile responses to NE (pA2 value) of 10.46 ± 0.85 for prazosin and 6.29 ± 0.18 for yohimbine. These data indicate a dominance of functional alpha 1 (α1) over alpha 2 (α2)-ARs in this tissue. Based on the inhibitory effects of chloroethylclonidine (CEC) on PE responses and the further reduction in sensitivity when nifedipine was added to the CEC, also in the presence of PE, we conclude that there is more than one α1-AR subtype, with a predominant role for α1B-ARs in phenylephrine responses. Stimulation of beta (β)-ARs, resulted in relatively small reductions in tone (the highest magnitude of response was 25.94 ± 6.46% of the papaverine maximum at 3×10−6 M isoproterenol); in addition, propranolol did not significantly alter tissue sensitivity to NE. Additional characterization of functional autonomic receptor populations in this circulatory bed will form a basis for future studies on circulatory dynamics in the mammary gland.  相似文献   

13.
The cardiopulmonary effects of the intravenous administration of clonidine (15 μg/kg), ST-91 (30 μg/kg) and diazepam (0.4 mg/kg) were compared in five healthy sheep using a randomized cross-over design, to determine whether the hypoxaemic effects of α2 adrenoceptor agonists are due to sedation, or to peripheral α2 adrenoceptor stimulation. All three drugs significantly lowered arterial oxygen tension (PaO2) levels within 2 min of their administration; however, clonidine and ST-91 produced long lasting and severe hypoxaemia with mean PaO2 levels of ≈40 mm Hg and 50 mm Hg (5.3 kPa and 6.6 kPa), respectively. The fall in PaO2 was considerably less with diazepam (63 mm Hg or 8.4 kPa at 2 min) and by 15 min the values did not differ from placebo treated animals. None of the drugs increased arterial carbon dioxide tension (PaCO2) levels when compared to saline treatment and the acid base variables did not show any significant change. A significant increase was recorded in the packed cell volume of the ST-91 treated group throughout the study. Within 2 min of their administration, all drugs caused a significant increase in mean arterial pressure (MAP) as compared to the placebo treated group. The MAP remained significantly increased for 5 and 60 min after clonidine and ST-91 treatment, respectively. The study shows that ST-91 and clonidine produce a greater degree of hypoxaemia than occurs with diazepam sedation, and that the hypoxaemic effect of α2 adrenoceptor agonists in sheep are mainly mediated by peripheral α2 adrenoceptors.  相似文献   

14.
Inhalt Der Einfluß, einer Ovarstimulation mit PMSG bzw. FSH auf die Entwicklung der Ovarialfollikel und die Kernreifestadien follikulärer, Oozyten wurde an 17 Färsen unter-sucht. Die Tiere erhielten entweder einmalig 2000 1E PMSG und 58 h danach 0,5 mg PGF2α (Gruppe 1, n = 8) oder hypophysäres Schweine-FSH (2 mal täglich über 4 Tage in abnehmender Dosierung, Gesamtdosis 885 1E) und 48 bzw 60 h nach der ersten FSH-Gabe 0,5 mg bzw. 0,25 mg PGF2α (Gruppe 2, n = 9) i.m. injiziert. 65 h nach der PGF2α-Applikation wurden die Ovarien der Färsen exstirpiert und alle Antralfollikel ab 2 mm Durchmesser einzeln aspiriert. Zu diesem Zeitpunkt waren zwischen den beiden Gruppen keine signifikanten Unterschiede (P > 0,05) in der mittleren Follikelanzahl (27,0 ± 14,7 in Gruppe 1 bzw. 22,4 ± 11,5 Follikel in Gruppe2), in der Gewinnungsrate von Cumulus-Oozyten-Komplexen (34,7 bzw. 43,1%) sowie in der Anzahl degenerierter follikulärer Oozyten (44,0 bzw. 50,6%) feststellbar. In beiden Behandlungsvarianten war der Anteil präovulatorischer Follikel geringer als der von nonovulatorischen Follikeln (30,6 zu 69.4% bzw. 47,5 zu 52,5%). Nach PMSG-Behandlung wurden im Vergleich zur FSH-Applikation erhöhte Anteile in Reifung befindlicher und reifer intakter Oozyten gefunden (26,7 bzw. 13,8%). Anhand der geprüften Parameter kann keine Überlegenheit einer der beiden Behandlungsvarianten abgeleitet werden.  相似文献   

15.
The aim of study was to correlate tumour necrosis factor-α (TNF) infused doses used with the TNF concentrations achieved and with the secretory function of both the ovary and the uterus in cows. We evaluated the concentrations of progesterone (P4), prostaglandin (PG)F2α, PGE2 nitric oxide (NO) and TNF in the jugular vein and vena cava caudalis as parameters of exogenous TNF action on the female reproductive tract. Aortae abdominalis of cows (n = 18) were infused with saline or two doses of TNF (luteolytic – 1 μg or luteotrophic – 10 μg). In the peripheral blood, 1 μg TNF concentrations achieved within the range of 30–45 pg/ml, and 10 μg TNF provoked a sharp increase in achieved concentrations at a range of 250–450 pg/mL). The TNF concentrations achieved in vena cava caudalis were five to six times higher than that in peripheral blood (p < 0.001). One microgram TNF increased PGF2α and NO (p < 0.001) and decreased P4 (p < 0.05). The higher TNF dose stimulated P4 and PGE2 (p < 0.01). TNF infusion at luteolytic dose achieved its concentrations at the physiological range previously observed in cows. Luteotrophic TNF dose achieved the concentrations in vena cava caudalis that are much higher than physiological level and were previously noted in pathological circumstances (i.e. mastitis , metritis ).  相似文献   

16.
A radioreceptor assay technique is described for the measurement of xylazine and medetomidine in sheep plasma. The assay was based on the displacement of tritiated clonidine from a 2-adrenoceptors in a rat brain homogenate by xylazine or medetomidine extracted from plasma. Plasma samples from sheep which had been given xylazine and medetomidine were treated with alumina to remove endogenous catecholamines which would otherwise have bound to α2-- adrenoceptors and interfered with the assay. The drugs were then extracted using chloroform, reconstituted in buffer and used to displace [3H]clonidine. The concentration of α2-agonist was calculated by reference to standard curves. The method had a detection limit of 2.5 ng/mL for xylazine and 0.24 ng/mL for medetomidine. The assay could also be used to detect metabolites capable of binding to α2-receptors.  相似文献   

17.
The pharmacokinetic properties of norfloxacin were determined in healthy pigs after single intramuscular (i.m.) and intravenous (i.v.) dosage of 8 mg/kg body weight After i.m. and i.v. administration, the plasma concentration-time graph was characteristic of a two-compartment open model. After single i.m. administration, norfloxacin was absorbed rapidly, with a t max of 1.46 ± 0.06 h. The elimination half-life ( t 1/2β) and the mean residence time of norfloxacin in plasma were 4.99 ± 0.28 and 6.05 ± 0.22 h, respectively, after i.m. administration and 3.65 ± 0.16 and 3.34 ± 0.16 h, respectively, after i.v. administration. Intramuscular bioavailability was found to be 53.7 ± 4.4%. Plasma concentrations greater than 0.2 μg/mL were achieved at 20 min and persisted up to 8 h post-administration. Maximal plasma concentration was 1.11 ± 0.03 μg/mL. Statistically significant differences between the two routes of administration were found for the half-lives of both distribution and elimination phases ( t 1/2α, t 1/2β) and apparent volume of distribution (Vd(area)). In pigs, norfloxacin was mainly converted to desethylenenorfloxacln and oxonorfloxacin. Considerable tissue concentrations of norfloxacin, desethylenenorfloxacin, and oxonorfloxacin were found when norfloxacin was administered intramuscularly (8 mg/kg on 4 consecutive days). The concentration of the parent fluoroquinolone in liver and kidney ranged between 0.015 and 0.017 μg/g on day 12 after the end of dosing.  相似文献   

18.
Strips of tracheal smooth muscle from 12 horses were contracted by carbachol in tissue baths under isometric conditions. This contraction (≅50% of maximum: EC50) was relaxed completely with adrenoceptor drugs. The only exception was clenbuterol, where the degree of relaxation was ≅90%. In all horses the EC50-value for isoprenaline (mean 1.6 × 10−8M) was less than that for adrenaline (mean 9.6 × 10− 8M) and noradrenaline (mean 1. 8 × 10- 6M). The potency ratio was 1 < 6 < 110 which indicates that the β2-subtype dominates among the β-adrenoceptors of equine airways. All preparations were also very sensitive to the specific and potent β2-receptor agonists clenbuterol (mean 5.7 × 10− 9M) and procaterol (mean 3.6 × 10−10M). No differences in EC50-values due to age, sex and breed were observed in this material. The standard deviation of the mean EC50-values seems to be larger for the specific β2-adrenoceptor agonists than for the unspecific. A reason for this could be differences in the pattern of the β-adrenoceptor population.  相似文献   

19.
Pharmacokinetics of enrofloxacin in newborn and one-week-old calves   总被引：4，自引：0，他引：4  
The pharmacokinetic behaviour of enrofloxacin was compared in four one-day-old and four one-week-old calves in order to find out if there were any age-related differences. Mean volume of distribution ( V d(ss)) and clearance ( Cl ) were significantly smaller in newborn calves: V d(ss) was 1.8 and 2.3 L/kg, while clearance was 0.19 and 0.39 L/kg.h in newborn and one-week-old calves, respectively. Mean elimination half-life ( t 1/2β) did not differ significantly in newborn and in one-week-old calves: mean t 1/2β was 6.6 h and 4.9 h, respectively. Enrofloxacin was metabolized to ciprofloxacin both by newborn and one-week-old calves, but the maximum concentration ( C max) of ciprofloxacin was lower and the time when maximum concentration was reached ( t max) later in newborn calves. We conclude that the dosage of enrofloxacin should be adjusted according to age when administered to very young calves.  相似文献   

20.
Pharmacokinetics of cefoperazone in horses   总被引：1，自引：0，他引：1  
The pharmacokinetics and bioavailabilty of cefoperazone (CPZ) were studied following intravenous (IV) and intramuscular (IM) administration of single doses (30 mg/kg) to horses. Concentrations in serum, urine and synovial fluid samples were measured following IV administration. CPZ concentrations in serum, synovial fluid and spongy bone samples were measured following IM administration. After IV administration a rapid distribution phase ( t 1/2(α):4.22 ± 2.73 min) was followed by a slower elimination phase ( t 1/2(β) 0.77 ± 0.19 h). The apparent volume of distribution was 0.68 ± 0.10 L/kg. Mean synovial fluid peak concentration was 5.76 ± 0.74 μg/mL. After IM administration a bioavailability of 42.00±5.33% was obtained. Half-life of absorption was 2.51 ± 0.72 min and t 1/2(β) was 1.52±0.15 h. The mean synovial fluid and spongy bone peak concentrations at 2 h after IM administration were 2.91±0.85 μg/mL and 5.56±0.70 μg/mL, respectively.  相似文献   

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